GHSA-2H9P-PP39-9929
Vulnerability from github – Published: 2026-08-10 15:33 – Updated: 2026-08-19 18:32In the Linux kernel, the following vulnerability has been resolved:
binfmt_misc: set have_execfd only once the interpreter is opened
load_misc_binary() raises bprm->have_execfd as soon as it sees the 'O' (or 'C') flag. This happens well before it opens the interpreter. If that open fails the flag stays set on the bprm. binfmt_misc is at the head of the format list so an interpreter open failure that returns -ENOEXEC lets the search fall through to a later format. This means it runs the matched binary directly having never staged an interpreter. So bprm->executable is NULL while have_execfd falsely claims a descriptor is present.
Consequently, begin_new_exec() dereferences the missing executable:
would_dump(bprm, bprm->executable);
and NULL derefs. Had it not, the hand-off later in the same function would have failed anyway. FD_ADD(0, bprm->executable) rejects a NULL file with -ENOMEM. Both sites are past the point of no return so the exec cannot be unwound either way.
This can be reached by unprivileged users as binfmt_misc can be mounted in user namespaces. So a user can register an 'O' entry whose interpreter lives on a FUSE mount, have the FUSE server fail the open with -ENOEXEC and execute a native ELF file that matches the entry.
have_execfd only means anything alongside the executable it describes which is not set until the interpreter has been opened and staged. So lets raise it there, next to execfd_creds, which is already set at that point. An open failure now leaves it clear, so the fallback format derives credentials from the binary and emits no AT_EXECFD, as it would for any native exec. The argv rewrite load_misc_binary() performs before the open is still not undone. This means the binary sees the interpreter path in argv[0] and its own path in argv[1] but that predates this change and only became observable once the exec stopped faulting.
{
"affected": [],
"aliases": [
"CVE-2026-68186"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-08-10T13:20:05Z",
"severity": null
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nbinfmt_misc: set have_execfd only once the interpreter is opened\n\nload_misc_binary() raises bprm-\u003ehave_execfd as soon as it sees the \u0027O\u0027\n(or \u0027C\u0027) flag. This happens well before it opens the interpreter. If\nthat open fails the flag stays set on the bprm. binfmt_misc is at the\nhead of the format list so an interpreter open failure that returns\n-ENOEXEC lets the search fall through to a later format. This means it\nruns the matched binary directly having never staged an interpreter. So\nbprm-\u003eexecutable is NULL while have_execfd falsely claims a descriptor\nis present.\n\nConsequently, begin_new_exec() dereferences the missing executable:\n\n would_dump(bprm, bprm-\u003eexecutable);\n\nand NULL derefs. Had it not, the hand-off later in the same function\nwould have failed anyway. FD_ADD(0, bprm-\u003eexecutable) rejects a NULL\nfile with -ENOMEM. Both sites are past the point of no return so the\nexec cannot be unwound either way.\n\nThis can be reached by unprivileged users as binfmt_misc can be mounted\nin user namespaces. So a user can register an \u0027O\u0027 entry whose\ninterpreter lives on a FUSE mount, have the FUSE server fail the open\nwith -ENOEXEC and execute a native ELF file that matches the entry.\n\nhave_execfd only means anything alongside the executable it describes\nwhich is not set until the interpreter has been opened and staged.\nSo lets raise it there, next to execfd_creds, which is already set at\nthat point. An open failure now leaves it clear, so the fallback format\nderives credentials from the binary and emits no AT_EXECFD, as it would\nfor any native exec. The argv rewrite load_misc_binary() performs before\nthe open is still not undone. This means the binary sees the interpreter\npath in argv[0] and its own path in argv[1] but that predates this\nchange and only became observable once the exec stopped faulting.",
"id": "GHSA-2h9p-pp39-9929",
"modified": "2026-08-19T18:32:09Z",
"published": "2026-08-10T15:33:39Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-68186"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/0f19d54e2524f0bf183b82f365ae4e49b4a2f788"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/1cd4e9b7967dab48c9f79a00b06ffff7208c0993"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/2dd0298905e97795a9c5ec30cf5b41975f821632"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/40c09b7a1d4e0a4866042c87c2bd911bb57566c8"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/5ccc99d58f94fad258c9c375715b3974e48620e8"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/a261dc49d99681c9c71f38d16e31812dc3e30412"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/a8e9e9450df44e9dd529ec5beff283f48f4f4b97"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/bbf5f639918dc011aaf60aab8480218758ee68c5"
}
],
"schema_version": "1.4.0",
"severity": []
}
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.